Donald Trump arrives to addresses a joint session of the U.S. Congress: Getty

A leading climatologist has warned US democracy is under attack from the “uninhibited use of lies, false statements and bad science”, as he urged people to take part in public demonstrations in support of science.

In an article for the website Wired, Dr Peter Gleick, co-founder of the Pacific Institute in California, said leading members of Trump administration rejected the “undeniable reality of climate change”, evolution, the science about vaccines, and the need to study gun violence.

And he said he had taken to carrying a copy of the US Constitution in his briefcase to help remind himself that it guarantees the right to peacefully protest.

At the recent American Association for the Advancement of Science’s annual meeting, its chief executive Rush Holt said some members had expressed fear that the US could become like the Soviet Union, where ideology carried more weight than hard evidence.

Clearly sharing similar concerns, Dr Gleick, a member of the US National Academy of Sciences, said he planned to attend both the March for Science and the Climate March in April.

The demonstrations were prompted by Donald Trump’s stance on science and follow the Women's Marches around the world held in response to a man who bragged about being able to sexually assault women because he was a celebrity becoming US President. He later insisted he had never actually done so and his remarks were "locker-room talk".

“A disturbing array of fundamental social and human values are under assault in the United States,” Dr Gleick wrote.

“These values – basic human rights, amicable international relationships, environmental justice, free speech, separation of church and state, an open and independent media, and more – form the bedrock of what makes our country special.

“Yet these values are being undermined in an unprecedented assault by the Trump administration and by politicians who see an opportunity for an unprincipled massive power grab.

“One tool being used in this assault on democracy is the uninhibited use of lies, false statements, blatant and intentional misrepresentations of fact, and bad science.

“This is evident in the rejection of the undeniable reality of climate change by many of Trump’s top appointees, the promotion to power of individuals who reject the fact of evolution in favour of pseudoscience and religious fundamentalism, the spreading of bad medical science around the proven safety of vaccines, and the refusal to study the health risks of guns.”

He said he had found the news over the past few weeks “frightening”.

“I have colleagues in countries targeted by travel and religious bans. My work uses scientific data collected, managed, and now potentially censored or hidden by federal agencies,” Dr Gleick said.

“I see Congressional representatives and committees seek out bad science to support predetermined and ideological positions, and then threaten scientists who challenge them.”

Scientists tended to fear their work could become “tainted by politics”, he said, adding the rewards for expressing political opinions were few.

“But when the time comes to speak, to stand up, those of us who can must do so. That time has come,” he said.

“When politics threatens fundamental social values and principles, the defence of those values and principles becomes an over-riding priority.”

Dr Gleick said he had been tear-gassed when protesting against the Vietnam War in the 1970s and had also marched in opposition to the Iraq War in 2003.

But he said: “The current threats to society are far worse.

“These public demonstrations offer an opportunity for all Americans, not just scientists, to stand up for science, objectivity, facts, and truth, at a time when telling the truth is becoming a threatened, radical act.”

The March for Science is being held on 22 April. The main event is in Washington DC but others are being held across the US and also in other countries, including the UK.

The People’s Climate March will be held on 29 April in Washington and other cities in the US.